Burgess Shale fossils illustrate the origin of the mandibulate body plan

  title={Burgess Shale fossils illustrate the origin of the mandibulate body plan},
  author={C{\'e}dric Aria and Jean‐Bernard Caron},
Retracing the evolutionary history of arthropods has been one of the greatest challenges in biology. During the past decade, phylogenetic analyses of morphological and molecular data have coalesced towards the conclusion that Mandibulata, the most diverse and abundant group of animals, is a distinct clade from Chelicerata, in that its members possess post-oral head appendages specialized for food processing, notably the mandible. The origin of the mandibulate body plan, however, which… 

Fossils from South China redefine the ancestral euarthropod body plan

Sklerolibyon and other jianfengiids expand the disparity of megacheirans and suggest that the common euarthropod ancestor possessed a remarkable phenotypic variability associated with the externalized cephalon, as well as endopods that were already heptopodomerous, which differs from previous hypotheses and observations.

A middle Cambrian arthropod with chelicerae and proto-book gills

Fossil material from the middle Cambrian Burgess Shale is used to show that Mollisonia plenovenatrix possessed robust but short chelicerae that were placed very anteriorly, between the eyes, which suggests that chelicers evolved a specialized feeding function early on, possibly as a modification of short antennules.

A possible case of inverted lifestyle in a new bivalved arthropod from the Burgess Shale

Fibulacaris nereidis is unique in its carapace morphology and overall widens the ecological disparity of Cambrian arthropods and suggests that the evolution of a ‘bivalved’ carapACE and an upside-down lifestyle may have occurred early in stem-group crustaceans.

Fuxianhuiids are mandibulates and share affinities with total-group Myriapoda

In spite of their unrivalled ecological success, the origins of terrestrial mandibulates have long remained virtually unknown. In recent years, claims have been made based on phylogenetic results

A new species of early Cambrian arthropod reconstructed from exceptionally preserved mandibles and associated small carbonaceous fossils (SCFs)

Mandibulate arthropods (myriapods, hexapods and crustaceans) account for a major component of extant animal diversity but their origins remain unclear. Here, we re‐examine the record of exceptionally

Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale

It is construe that Waptia was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.

A Burgess Shale mandibulate arthropod with a pygidium: a case of convergent evolution

Cambrian bivalved arthropods are a polyphyletic group of carapace‐bearing arthropods that includes stem euarthropods, stem mandibulates and crustaceans. Here, we describe Pakucaris apatis gen. et sp.

Functional importance of the mandibular skeleto-muscular system in the bivalved arthropod Heterocypris incongruens (Crustacea, Ostracoda, Cyprididae)

Arthropods with a pair of mandibles (Mandibulata) emerged by the end of the Cambrian period. The mandible is one of the apomorphic characteristics of this monophyletic clade, which is composed of

An early Cambrian euarthropod with radiodont-like raptorial appendages

The phylogenetic reconstruction recovers Kylinxia as a transitional taxon that bridges Radiodonta and Deuteropoda, providing insights into the phylogenetic relationships among early euarthropods, the evolutionary transformations and disparity of frontalmost appendages, and the origin of crucial evolutionary innovations in this clade.



A large new leanchoiliid from the Burgess Shale and the influence of inapplicable states on stem arthropod phylogeny

A new leanchoiliid is described, Yawunik kootenayi gen. nov, based on 42 specimens from the newly discovered Marble Canyon locality of the Burgess Shale, which stresses the historical importance of polarization over data content in scenarios of early arthropod evolution and a pressing need to investigate the impacts of coding inapplicables, especially given the inflating effect of implied weights.

A palaeontological solution to the arthropod head problem

  • G. Budd
  • Environmental Science
  • 2002
It is shown that a group of previously problematic Cambrian arthropods from the Burgess Shale and Chengjiang faunas form a clade close to crown-group euarthropods, the group containing myriapods, chelicerates, insects and crustaceans, and two pre-oral appendages.

The Arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia

O. alata shows some similarities to the Crustacea, particularly the Branchiopoda, but the preservation of the features of the cephalon is inadequate to allow its affinities to be determined unequivocally.

Cephalic and Limb Anatomy of a New Isoxyid from the Burgess Shale and the Role of “Stem Bivalved Arthropods” in the Disparity of the Frontalmost Appendage

The diversity of frontalmost appendages in “stem bivalved” arthropods, distinct in its absence of clear clustering, is found to link the morphologies of “short great appendages,” chelicerae and antennules, and fits the hypothesis of an increase in disparity of the deutocerebral appendage prior to its diversification in euarthropods.

Cambrian bivalved arthropod reveals origin of arthrodization

A cladistic analysis resolved a new arthropod from the Tulip Beds locality of the Burgess Shale Formation as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming.

Specialized appendages in fuxianhuiids and the head organization of early euarthropods

The presence of a pair of specialized post-antennal appendages (SPAs) in the fuxianhuiid head, which attach at either side of the posteriorly directed mouth, behind the hypostome, indicates that antenniform deutocerebral appendages with many podomeres are a plesiomorphic feature of the ancestral euarthropod head.

Cambrian ‘Orsten’-type arthropods and the phylogeny of Crustacea

‘Orsten’ is a special type of anthraconitic, organic-rich, concretionary limestone which is intercalated in the Upper Cambrian Alum Shale of southern Sweden and is extended to embrace a type of lagerstatten with a particular type of fossil preservation, i.e. the three-dimensional preservation of phosphatized cuticle-bearing organisms.

Cambrian origins and affinities of an enigmatic fossil group of arthropods

A euthycarcinoid from marine strata in Argentina dating from the latest Cambrian period is described, extending the group's record back as much as 50 million years and demonstrating that morphological details were conserved in the transition to fresh water.

A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies.

The discovery of an extraordinary new soft-bodied fauna from the Burgess Shale is reported, and the presence of the stem arthropods Misszhouia and Primicaris, previously known only from the early Cambrian of China, suggests that the palaeogeographic ranges and longevity of Burgess Shales taxa may be underestimated.